1. Field of Invention
The present invention relates to a multi-view 3D image display method, which is mainly to propose a multi-view 3D image combination method and a slantwise strip parallax barrier structure design and optimization method without reducing a sub-pixel aperture ratio during display of a multi-view 3D image by using a planar display screen having sub-pixels in strip configuration and a slantwise strip parallax barrier, so as to achieve objectives of solving a direct cross-talk phenomenon and balancing a phenomenon of asymmetrical left and right viewing freedom at the same time. In addition, for display of a multi-view 3D image having a total view number greater than two, a multiple multi-view 3D image combination and display method is proposed, so as to achieve an objective of reducing the defect of discontinuous parallax jump.
2. Related Art
FIG. 1 is a schematic view of a planar display screen having R, G, and B sub-pixels arranged in horizontal strip configuration. The planar display screen 1 may be a liquid crystal screen, plasma screen, or organic light emitting diode (OLED) screen, which is formed of (N×M) R, G, and B sub-pixels and has a feature of horizontal strip configuration. N is a total number of sub-pixels in a horizontal direction (X axis) of the display screen, and M is a total number of sub-pixels in a vertical direction (Y axis) of the display screen. j and i are the indexes of a horizontal position and a vertical position of a single sub-pixel respectively, where 0≦j≦N−1 and 0≦i≦M−1. The single sub-pixel has a size of PH×PV, where PH is a horizontal width of a sub-pixel and PV is a vertical height of a sub-pixel. By subtracting a black space 2 between sub-pixels (which is usually formed of a non-luminous material and is black, for example, which is formed of black photoresist on a liquid crystal display panel and referred to as a black matrix), the effective luminous size of the single sub-pixel is H×V. It is defined that a horizontal aperture ratio RH and a vertical aperture ratio RV are respectively as follows:RH=H/PH  (1), andRV=V/PV  (2).
The so-called horizontal strip configuration means that in any arbitrary horizontal scan line, the R, G, and B sub-pixels are arranged in a sequence of R, G, and B in a horizontal direction to form a strip structure with color distribution; while in a vertical direction, sub-pixels of a same color form a single-color strip structure.
In addition, a planar display screen (not shown) having R, G, and B sub-pixels in vertical strip configuration is also commercially available. The so-called vertical strip configuration is that in any arbitrary vertical scan line, the R, G, and B sub-pixels are arranged in a sequence of R, G, and B in a vertical direction to form a strip structure with color distribution; while in a horizontal direction, sub-pixels of the same color form a single-color strip structure.
Generally, for a planar display screen having R, G, and B sub-pixels in horizontal strip configuration, the size of a single sub-pixel thereof has a relation of PH≦PV. For a planar display screen having R, G, and B sub-pixels in vertical strip configuration, a size of a single sub-pixel thereof has a relation of PH≧PV. Regardless of the configuration direction of R, G, and B sub-pixels, for the two mentioned planar display screens above, it is commercially referred to as a planar display screen having R, G, and B sub-pixels in strip configuration in short. For simplicity of drawings and illustrations, in the present invention, a planar display screen having R, G, and B sub-pixels in horizontal strip configuration is taken as an example for illustrating effects of the present invention.
When the planar display screen 1 is used for displaying a 3D image, for example, as disclosed in U.S. Pat. No. 7,317,494 B2 (as shown in FIG. 2 to FIG. 9), a slantwise strip parallax barrier device is used to reduce the moire and decrease the cross-talk, so as to achieve an objective of displaying a 3D image.
FIG. 2 is a schematic view of a structure of a conventional 4-view combined 3D image. In the mentioned U.S. Patent, a 4-view combined 3D image is taken as an example for illustrating effects thereof. In the 4-view combined 3D image 4, four single view images {circle around (0)}, {circle around (1)}, {circle around (2)}, and {circle around (3)} having a parallax effect form a smallest 3D image unit 6 or 7 by taking a sub-pixel as an unit according to a sequence of {circle around (0)}, {circle around (1)}, {circle around (2)}, and {circle around (3)}. In a horizontal direction, the smallest 3D image units 6 are repetitively arranged, so as to form a horizontal image of the multi-view combined 3D image 4. In a vertical direction, the smallest 3D image units 6 and 7 in the adjacent upper and lower rows are arranged in a manner of relatively displacing by a width of a sub-pixel.
FIG. 3 is a schematic view of a structure of a conventional 4-view slantwise strip parallax barrier. A 4-view slantwise strip parallax barrier 10 disclosed in the mentioned U.S. Patent is formed of a plurality of slantwise strip transparent components 11 and a plurality of slantwise strip opaque components 12. The slantwise strip transparent component 11 has an aperture width B4, which may have the relation of the following formula:B4=PH  (3).
A slant angle θ of the 4-view slantwise strip parallax barrier 10 may be represented by the following formula:tan θ=PH/PV  (4).
FIG. 4 is a schematic view of display principles of the conventional 4-view combined 3D image. For the 4-view combined 3D image 4 (that is, the image formed of {circle around (0)}, {circle around (1)}, {circle around (2)}, and {circle around (3)}) displayed on the planar display screen 1, the 4-view slantwise strip parallax barrier 10 may individually separate the 4-view combined 3D image 4 into four single view images {circle around (3)}, {circle around (2)}, {circle around (1)}, and {circle around (0)} at multiple optimum viewing points P3, P2, P1, and P0 on an optimum viewing distance Z0. Generally speaking, in the design of a parallax barrier, an interval between the optimum viewing points is made equal to an interpupillary distance (IPD) LE. Therefore, as long as a viewer places the left and right eyes 15 respectively at proper positions, that is, (P3,P2), or (P2,P1), or (P1,P0), the viewer may view a 3D image without cross-talk. In other words, for the display of a 4-view 3D image, three optimum viewing positions (P3,P2), (P2,P1), and (P1,P0) are provided, so the viewer may view the 3D image without cross-talk. Therefore, the four optimum viewing points P3, P2, P1, and P0 form a group of viewing zones. Theoretically, on the optimum viewing distance Z0, an infinite number of groups of viewing zones may exist. However, limited by the optical characteristics of the display screen (for example, a liquid crystal screen) and the parallax barrier (for example, a liquid crystal parallax barrier), usually only several groups of viewing zones exist.
FIG. 5 is a schematic view of a direct cross-talk phenomenon. For the above-mentioned 4-view slantwise strip parallax barrier 10, in a planar display screen having a relatively large aperture ratio (with a sub-pixel width PH), as the slantwise strip transparent component 11 (having an aperture width B4=PH) spans two sub-pixels at the same time, that is, a phenomenon of spanning two view images occurs. Therefore, the cross-talk directly occurs (hereinafter, referred to as direct cross-talk), such that a high-quality 3D image is unable to be displayed.
FIG. 6 is a schematic view of a method for solving direct cross-talk in the conventional patent. For the above-mentioned defects, the solution proposed in the U.S. Patent is to properly reduce an aperture ratio of the planar display screen, so as to achieve an objective of reducing the direct cross-talk. Therefore, for the planar display screen 1, an effective luminous size of a single sub-pixel is reduced to H′×V′, which satisfies the relation in the following formula:H′=PH×(PV−V′)/PV  (5).
According to the formula (5), when the effective luminous size is H′=PH/2 and V′=PV/2, the problem of direct cross-talk is solved, and the requirement of minimum moire is satisfied. That is, when both the horizontal aperture ratio RH and the vertical aperture ratio RV are 0.5, the optimum effects are achieved.
In conclusion, in the U.S. Pat. No. 7,317,494 B2, mainly two methods are proposed: (1) the slantwise strip parallax barrier (having the structure denoted by the formulas (3) and (4)); and (2) setting both the horizontal aperture ratio RH and the vertical aperture ratio RV of the sub-pixel on the planar display screen to 0.5, so the objectives of solving the direct cross-talk and reducing the moire are solved at the same time. However, the current commercially available mainstream planar display screens (for example, thin-film transistor (TFT) liquid crystal screens) are all in pursuit of a technical aim of increasing the sub-pixel aperture ratio, and planar display screens having both RH and RV being 0.5 are no more unavailable. Even for a planar display screen adopting RH=RV=0.5, when the slantwise strip transparent component has an aperture width B4=PH, the phenomenon of moire may be properly moderated, but the brightness of the image is severely decreased and the horizontal viewing freedom is also reduced to a great extent. In addition, for the display of a multi-view combined 3D image having a total view number greater than 2, a solution for reducing discontinuous parallax jump is also unavailable.
The so-called horizontal viewing freedom refers to a horizontal viewing range without cross-talk (referring to ROC Patent Applications No. 098128986 and No. 099107311), that is, an allowable maximum deviation range as the eyes deviate from the above optimum viewing points without seeing cross-talk.
FIG. 7 is a schematic view of changes of relative viewing angles and positions between the parallax barrier and the multi-view combined 3D image when the eyes deviate to the left. For a viewer with two eyes at the optimum viewing points (for example: the right eye is located at P0, where an image without cross-talk {circle around (0)} is perceived), when a viewing position of the viewer deviates to the left, the change of the perceived multi-view combined 3D image due to the change of the viewing angle is equivalent to the multi-view combined 3D image perceived after the parallax barrier displaces to the right. Therefore, for the multi-view combined 3D image at a position 16 indicated by the arrow (for example, a bottom end of a single sub-pixel), as the parallax barrier slants to the right, when the viewing position deviates to the left, the cross-talk occurs immediately, that is, the image at {circle around (1)} is perceived. In FIG. 8 and FIG. 9, the phenomenon of cross-talk resulted from the deviation of the viewing position may be analyzed more clearly.
FIG. 8 is a schematic view of a multi-view combined 3D image viewed by the right eye before the viewing position is changed. For the right eye 15 at P0, and for the aperture 11 of the parallax barrier at the position 16 indicated by the arrow in FIG. 7, the image 21 perceived by the right eye 15 is only the image of the view {circle around (0)}, which is in a state of no cross-talk.
FIG. 9 is a schematic view of a multi-view combined 3D image viewed by the right eye after the viewing position moves to the left. When the right eye 15 moves to the left by a displacement amount ΔP0, through the aperture 11 of the parallax barrier, the image 22 of the view {circle around (0)} and {circle around (1)} is perceived by the right eye 15 at the same time, so a cross-talk phenomenon occurs. In addition, for the images 21 and 22 viewed before and after movement, in fact, due to changes of imaging spatial frequencies, a phenomenon of moire also occurs.
In addition, in the mentioned patent, for the display of a multi-view 3D image having a total view number greater than 2, a phenomenon of discontinuous parallax jump also occurs, and yet no solution has been proposed.
FIG. 10 is a schematic view of the cause of the phenomenon of discontinuous parallax jump. In the following, a 4-view is taken as an example for illustration. Generally speaking, no matter whether a real-view image or an animated drawing is used as a source of a 3D image, the multi-view image is produced by making optical axes of four cameras 63, 62, 61, and 60 (angles of the optical axes are respectively: Ω3, Ω2, Ω1, and Ω0) converge at a same point for a shot object 50, and setting an equal shooting-angle ΔΩi, so as to capture single-view images {circle around (3)}, {circle around (2)}, {circle around (1)}, and {circle around (0)}. The above image shooting process is generally referred to as a convergent 3D photography. The so-called equal shooting-angle means that the angular interval between adjacent optical axes is a constant. That is, the equal shooting-angle ΔΩi is as defined in the following formula:ΔΩi=∥Ω3−Ω2∥=∥Ω2−Ω1∥=∥Ω1−Ω0∥  (6).
Therefore, as shown in FIG. 4, through the display of the 4-view combined 3D image, three optimum viewing positions (P3,P2), (P2,P1), and (P1,P0) can be provided to the viewer. The viewers at the three optimum viewing positions may respectively view 3D images with different viewing angles. That is, the 3D image with the viewing angle Ω32 may be viewed at (P3,P2), the 3D image with the viewing angle Ω21 may be viewed at (P2,P1), and the 3D image with the viewing angle Ω10 may be viewed at (P1,P0). For the viewing angles Ω32, Ω21, and Ω10, an equal shooting-angle ΔΩ0 may be defined, for example, as represented by the following formula:ΔΩ0=⊕Ω32−Ω21∥=∥Ω21−Ω10∥  (7).
The so-called phenomenon of discontinuous parallax jump means that as the equal shooting-angle ΔΩo is too large, the viewer may easily find that the 3D image of the shot object 50 is presented with changes of discontinuous angles when changing the optimum viewing position in the horizontal direction, thereby causing discomfort in viewing. Generally, the ΔΩo is reduced (that is, the ΔΩi is reduced to weaken the parallax effect) to reduce the phenomenon of discontinuous parallax jump; however, this method severely affects the sense of reality (that is, 3D sense) of the 3D image.
In conclusion, although the major technology (of reducing the aperture ratio of the sub-pixel on the planar display screen) proposed in the U.S. Pat. No. 7,317,494 B2 may properly reduce the phenomenon of moire, the following situations occur: (1) the brightness of the image is reduced; (2) the horizontal viewing freedom is greatly reduced; and (3) the defects such as the discontinuous parallax jump still exist. In addition, only text description is proposed for the combination of the multi-view 3D image, and even incorrect design (B4=PH) is proposed for the basic structure of the slantwise strip parallax barrier. Therefore, for the combination of the multi-view 3D image and the structure design of the slantwise strip parallax barrier, the patent also fails to propose a generally used and specific method to adapt to applications of an arbitrary view number.